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N Petrovic

Publications and source records attributed to N Petrovic.

15 recordsLinked to original sources
PubMed2006

Topological quantum computing with only one mobile quasiparticle.

In a topological quantum computer, universal quantum computation is performed by dragging quasiparticle excitations of certain two dimensional systems around each other to form braids of their world lines in 2 + 1 dimensional space-time. In this Letter we show that any such quantum computation that can be done by braiding n identical quasiparticles can also be done by moving a single quasiparticle around n - 1 other identical quasiparticles whose positions remain fixed.

Journal Article↗
PubMed2006

Radioimmunoscintigraphy of colorectal carcinomas with three different radiopharmaceuticals.

The aim of the study was evaluation of the clinical reliability of the immunoscintigraphy for the detection of metastases and recurrences of colorectal carcinomas using three different radiopharmaceutical substances. With IMACIS 1, the number of true negative findings (TN) was 4/7 and true positive (TP) 3/7, while in one patient, the results of immunoscintigraphy significantly influenced the therapeutical management. With INDIMACIS 19-9, there were 2/8 TN and 6/8 TP. In three patients, immunoscintigraphy results influenced patient further management. With ONCOSCINT in 2 patients findings were TN, in one FN and in one FP. In 3 patients, immunoscintigraphy influenced the management of the patient. Other imaging methods (CT, US, MRI) have advantage in detection of liver metastases, while immunoscintigraphy is more specific for the assessment of reccurences of the abdominal tumors. Thus immunoscintigraphy should be applied in patients with suggested recurrences and inconclusive outcome of routine diagnostic workup.

Adenocarcinoma↗
PubMed2005

Rupestris stem pitting associated virus isolates are composed by mixtures of genomic variants which share a highly conserved coat protein.

Broad spectrum primers were used to amplify a fragment comprising the CP gene and putative ORF6 by RT-PCR from ds-RNA templates originating from 46 Portuguese varieties, totalling 190 samples, including some wild Vitis ssp sylvestris vines, and 2 vines from Slovenia. SSCP analysis was used as a preliminary screen to avoid cloning and sequencing very similar variants. Four groups of variants were recognized. In pair wise comparisons between nucleotide sequences the minimal homology found was 81%. In case of the cultivated varieties, no relationship could be seen between the phylogenetic groups and geographic origin or grape variety. Several isolates were found harbouring mixed infections with genomic variants from different groups, but the mixing did not lead to an extensive recombination between them. The deduced amino-acid sequences revealed a conserved CP subjected to strong purifying selection pressure. Analysis of the selection pressure operating on the putative ORF6 suggests that this ORF does not exist. Previously produced polyclonal antiserum raised against the recombinant CP of RSPaV expressed in Escherichia coli was shown to be able to detect all four groups of variants of RSPaV included in this study, which might enable the diagnosis of the virus on a serological basis.

Capsid Proteins↗
PubMed2005

The activities of antioxidant enzymes and monoamine oxidase and uncoupling protein 1 content in brown fat of hypo- and hyperthyroid rats.

We have studied the activities of antioxidant enzymes (AOE), namely, copper-zinc superoxide dismutase (CuZnSOD), manganese superoxide dismutase (MnSOD), and catalase (CAT), and the activity of catecholamine-degrading enzyme monoamine oxidase (MAO) and uncoupling protein 1 (UCP1) content in brown fat (BF) of hypo- and hyperthyroid rats. We found that hypothyroidism decreased BF UCP1 content and increased MAO, MnSOD, and CAT activities. T3 increased UCP1 content and MnSOD activity and decreased CuZnSOD, MAO, and CAT activities, while T4 significantly altered (decreased) only CAT activity. This study shows that UCP1 content and MAO and AOE activities in rat BF are notably affected by changed thyroid status.

Adipose Tissue, Brown↗
PubMed2001

Critical roles of a cyclic AMP responsive element and an E-box in regulation of mouse renin gene expression.

Mouse As4.1 cells, obtained after transgene-targeted oncogenesis to induce neoplasia in renal renin expressing cells, express high levels of renin mRNA from their endogenous Ren-1(c) gene. We have previously identified a 242-base pair enhancer (coordinates -2866 to -2625 relative to the CAP site) upstream of the mouse Ren-1(c) gene. This enhancer, in combination with the proximal promoter (-117 to +6), activates transcription nearly 2 orders of magnitude in an orientation independent fashion. To further delimit sequences necessary for transcriptional activation, renin promoter-luciferase reporter gene constructs containing selected regions of the Ren-1(c) enhancer were analyzed after transfection into As4.1 cells. These results demonstrate that several regions are required for full enhancer activity. Sequences from -2699 to -2672, which are critical for the enhancer activity, contain a cyclic AMP responsive element (CRE) and an E-box. Electrophoretic mobility shift assays demonstrated that transcription factors CREB/CREM and USF1/USF2 in As4.1 cell nuclear extracts bind to oligonucleotides containing the Ren-1(c) CRE and E-box, respectively. These two elements are capable of synergistically activating transcription from the Ren-1(c) promoter. Moreover, mutation of either the CRE or E-box results in almost complete loss of enhancer activity, suggesting the critical roles these two elements play in regulating mouse Ren-1(c) gene expression. Although the Ren-1(c) gene contains a CRE, its expression is not induced by cAMP in As4.1 cells. This appears to reflect constitutive activation of protein kinase A in As4.1 cells since treatment with the protein kinase A inhibitor, H-89, caused a significant reduction in Ren-1(c) gene expression and this reduction is mediated through the CRE at -2699 to -2688.

Animals↗
PubMed2001

A simple assay for a human serum phospholipase A2 that is associated with high-density lipoproteins.

Phospholipase A2 (PLA2) activity is usually assayed with expensive radioactive or chromogenic substrates unsuitable for performing large numbers of assays. We have designed a simple microplate assay for human serum PLA2 using the chromogenic substrate 4-nitro-3-octanoyloxy-benzoic acid. Using this substrate, serum PLA2 activity was similar to that measured with the previously characterized chromogenic phospholipid substrate 1,2-bis-heptanoylthio-glycerophosphocholine. However, the assay described here appears to be more sensitive. The mean PLA2 activity in serum from healthy volunteers (n = 30) measured by this assay was 10.4 +/- 1.6 micromol x h(-1) x ml(-1). The assay is reproducible and is suitable for the analysis of large numbers of samples in a clinical setting. We have also demonstrated that 94% of the PLA2 activity in normal human serum is associated with high-density lipoproteins and that serum PLA2 activity is positively correlated with the lipoprotein parameters total triglyceride (P < 0.0001), total cholesterol (P < 0.0001), and atherogenic index (P = 0.008). The serum PLA2 activity was calcium dependent and was inhibited by the serine protease inhibitor 3,4-dichloroisocoumarin (EC(50) = 0.4 mM). The PLA2 activity characterized here is unlikely to be due to plasma platelet-activating factor acetylhydrolase or low molecular weight His-Asp sPLA2, and may represent a new sPLA2 type.

Chromatography, Gel↗
PubMed1997

Biosynthesis of renin in mouse kidney tumor As4.1 cells.

As4.1, a renin-expressing cell line isolated from a mouse renal tumor, was characterized for synthesis, processing, storage and secretion of renin polypeptides. Metabolic labeling, immunoprecipitation and SDS/PAGE analysis revealed that renin was secreted into the culture supernatant predominantly in the form of prorenin which migrated as products of 42-47 kDa. The predominant intracellular renin was processed into two chains, of 33-34 and 5 kDa. N-glycanase treatment removed N-linked oligosaccharides and yielded products of 41 kDa for prorenin and 31-32 kDa for the heavier chain of two-chain renin. The N-terminus of the constitutively secreted prorenin was determined by automated Edman degradation to be Leu22 while the N-terminus of the heavy chain was Ser72. Renin polypeptides constituted 3.1 +/- 1.4% (mean percentage of total precipitable radioactivity +/- SD) of de-novo-synthesized protein secreted into the medium and 0.2 +/- 0.17% retained intracellularly. Extrapolation of renin activity assays suggest that a single cell stores approximately 680 fg of active renin. A slow incremental release into the medium of processed renin heavy chain was detected by immunoprecipitation and SDS/PAGE. Renin activity assays confirmed the release of approximately 4 fg prorenin and 0.32 fg active renin cell(-1) h(-1). Indirect immunofluorescence demonstrated intracellular renin to be distributed in a punctate pattern. Renin was found to be colocalized with the lysosomal marker, beta-glucuronidase, by double-fluorescent labeling. These cells have enabled characterization of glycosylated mouse renin-1 and may prove a valuable tool for studying intracellular trafficing of renin and associated processing enzymes.

Animals↗
PubMed1997

Downregulation of renin gene expression by interleukin-1.

The As4.1 cell line was established from a mouse kidney tumor by transgene-targeted tumorogenesis. These cells express high levels of renin mRNA from their endogenous renin gene and release approximately eightfold-more prorenin than active renin in culture. Levels of renin mRNA in As4.1 cells are decreased in a dose-dependent manner by the addition of physiological concentrations of cytokine interleukin-1 to the media. Stability of renin mRNA and initial rates of release of active renin and prorenin were not significantly altered by interleukin-1. In contrast, transcription initiated from a construct that consisted of 4.1 kilobases of renin 5' flanking sequence fused to a reporter gene (chloramphenicol acetyltransferase) was markedly inhibited by interleukin-1. On the basis of our findings, we conclude that downregulation of renin synthesis caused by interleukin-1 occurs primarily at the level of transcription and that DNA sequence or sequences mediating that effect are positioned within 4.1 kilobases upstream of the renin gene. The physiological relevance of this regulation is related to the events that occur during septic shock, characterized by hypotension, cardiovascular collapse, multiple organ failure, and high mortality. Unexpectedly, hypotension associated with septic shock does not lead to activation of the renin-angiotensin system. The hypotension in septicemia is believed to be mediated by the combined action of many modulators including cytokines, and data presented here suggest direct involvement of interleukin-1 in this process.

Animals↗
PubMed1996

Identification of an apo-superoxide dismutase (Cu,Zn) pool in human lymphoblasts.

Copper incorporation (64Cu(II)) into Cu,Zn-superoxide dismutase (SOD) was studied in human lymphoblasts. Rapid incorporation of copper with a proportionate increase in SOD activity was detected. No copper incorporation or SOD activation was detected when 64Cu(II) was added to cell cytosols rather than to intact cells. Thus, incorporation of 64Cu was not due to isotopic exchange. Cycloheximide had no significant effect on copper incorporation and activation of SOD when the data were corrected for total cell copper. Thus, the data were consistent with copper incorporation into a preexisting apoSOD pool rather than newly synthesized SOD, and no new SOD synthesis was detected over a 15-h incubation period. The size of the apoSOD pool was estimated to be approximately 35% of the total SOD in lymphoblasts. When cells were preincubated for 15 h with excess copper (15 microM Cu(II)), the size of the apo pool markedly decreased but was not eliminated, suggesting that the apoSOD was not due to copper deficiency. These experiments also indicated that newly arrived copper was preferentially incorporated into the apoSOD pool, while the function(s) of an apoSOD pool remains unknown. Copper binding to apoSOD may provide a rapid protective response against copper toxicity.

Copper↗
PubMed1996

Copper incorporation into superoxide dismutase in Menkes lymphoblasts.

The incorporation of copper into Cu,Zn-superoxide dismutase (SOD) was examined in Menkes lymphoblasts that express a genetic defect of copper metabolism. SOD activity was approximately 40% higher in Menkes than normal lymphoblasts. Since Menkes lymphoblasts contain elevated copper levels, the higher SOD activity is most likely due to near copper saturation of an apoSOD pool that is in normal lymphoblasts. Cycloheximide markedly inhibited 64Cu(II) incorporation into SOD in Menkes lymphoblasts under conditions in which no significant, de novo synthesis of SOD protein was detected with normal lymphoblasts. The maximal amount of 64Cu incorporation into newly synthesized SOD in Menkes lymphoblasts was approximately equal to the maximal amount of 64Cu that could be incorporated into the apoSOD pool in normal lymphoblasts. The increased synthesis of SOD in Menkes lymphoblasts may play a protective role against copper toxicity in Menkes lymphoblasts. The protonophore, CCCP markedly inhibited 64Cu incorporation into SOD in both normal and Menkes lymphoblasts, which is consistent with 64Cu incorporation into SOD within a membrane-bounded compartment in both cell types. When 64Cu-incorporation into SOD was blocked with CCCP, copper accumulated in a Superose column fraction that contains S-adenosylhomocysteine hydrolase (SAHH), which has a high affinity for copper. SAHH may play a role in delivering copper to SOD.

Carbonyl Cyanide m-Chlorophenyl Hydrazone↗
PubMed1996

Role of proximal promoter elements in regulation of renin gene transcription.

Mouse As4.1 cells, obtained after transgene-targeted oncogenesis to induce neoplasia in renal renin-expressing cells, express high levels of renin mRNA from the endogenous Ren-1(c) gene. We have used these cells to characterize the role of the Ren-1(c) proximal promoter (+6 to -117) in the regulation of renin gene transcription. It was found that 4.1 kilobases (kb) of Ren-1(c) 5'-flanking sequence, in combination with the proximal promoter, are required for strong activation (approximately 2 orders of magnitude over the basal level of the promoter alone) of the chloramphenicol acetyltransferase reporter in transfection assays. Within the 4.1-kb fragment, a 241-base pair region was identified that retains full activity in an orientation-independent manner in combination with the promoter. The resulting transcripts initiate at the normal renin start site. Electrophoretic mobility shift assays identified a sequence at approximately position -60 in the promoter region that binds nuclear proteins specific for renin-expressing As4.1 cells. Mutations in this sequence, which disrupt binding of nuclear protein(s), completely abolish activation of transcription by the 4. 1-kb fragment. Activation of transcription by the 241-base pair enhancer was still observed, although it was diminished in magnitude (60-fold over the mutated promoter alone). We present a model derived from the current data that suggests that regulation of renin expression is achieved through cooperation of transcription factors binding at the proximal promoter element and a distal enhancer element to abrogate or override the effects of an intervening negative regulatory region.

Animals↗
PubMed1995

Identification of a major hepatic copper binding protein as S-adenosylhomocysteine hydrolase.

The properties of a mouse liver copper binding protein (CuBP) and human placental S-adenosylhomocysteine hydrolase (SAHH) were compared to test the hypothesis that CuBP is SAHH. CuBP and SAHH migrated identically on SDS-polyacrylamide gel electrophoresis gels, and their 48-kDa monomers both self-associate to tetramers. Human placental SAHH cross-reacted with polyclonal antibodies to mouse liver CuBP, and CuBP from mouse liver cross-reacted with two monoclonal antibodies to human placental SAHH. A third monoclonal antibody to human placenta SAHH reacted weakly with the mouse liver protein but well with CuBP from human lymphoblasts. NAD(+)-activated CuBP has high SAHH enzymatic activity. Moreover, human placental SAHH, like mouse liver CuBP, has a single high affinity copper binding site per 48-kDa subunit. Thus, the data confirm that CuBP is SAHH, and SAHH is proposed to be a bifunctional protein with roles in sulfur-amino acid metabolism and copper metabolism. The copper binding activity of SAHH is proposed to play a significant role in the intracellular distribution of copper, and SAHH enzymatic activity may influence copper metabolism through its role in cysteine biosynthesis from methionine.

Adenosylhomocysteinase↗
PubMed1989

[Treatment using Motilium of gastro-esophageal reflux associated with respiratory manifestations in children].

Eighteen children aged 1 month to 12 years 8 months (mean age, 4.9 years) with pH-metry proven gastroesophageal reflux (GOR)-associated chronic respiratory disorders were treated with Motilium, 2 mg/kg/d in four divided doses, for three months. The incidence of each of the respiratory manifestations decreased, and their cumulative score improved significantly at the end of the treatment period. Patient daily self-assessment scores also fell, but not significantly. Twenty-one hour pH recordings showed a significant reduction in the duration of nocturnal episodes below 4 (2.8 +/- 0.9% versus 8.2 +/- 2.6%, p less than 0.05). No side effects were recorded. Domperidone provides satisfactory control of nocturnal GOR and therefore emerges as a valuable agent for the treatment of chronic GOR-associated respiratory disorders in childhood.

Asthma↗
PubMedDate not supplied

Radioimmunodetection of colorectal carcinoma.

BACKGROUND/AIMS: The aim of the study is detection of the recurrences and metastases of colorectal carcinomas using 111In-labeled antibodies B72.3. METHODOLOGY: Fourteen patients underwent planar immunoscintigraphy and/or tomoscintigraphy. RESULTS: With tomography in comparison to planar scintigraphy, we can access better distinction of tumor and estimation of its size. Other imaging methods (computed tomography, ultrasonography) have an advantage in detection of liver metastases, while immunoscintigraphy is more specific for the assessment of malignant abdominal tumors and extrahepatic metastases. CONCLUSIONS: The first results point out that Oncoscint CR-103 can be useful in diagnosis of recurrences and metastases of colorectal carcinoma, viability assessment after radiotherapy and in the choice of the adequate surgical treatment in dependence of the spread of the disease.

Adenocarcinoma↗